Food-safe glaze guide and checklist

What makes a glaze food safe

A fired glaze is a kind of glass, and every glaze dissolves very slightly in contact with food and drink. Digitalfire's Tony Hansen explains that some glazes dissolve far more than others: badly balanced recipes, high loads of metal colourants, and glazes containing lead, barium or lithium are the ones to worry about, especially with hot, acidic or long contact. A clear or white glaze made only from harmless materials is much less of a concern.

• Fire it to maturity. A glaze that has not melted well is one of Digitalfire's warning signs, so fire to the cone the glaze and clay are made for and check it with witness cones on the cone chart.
• Use a liner glaze inside. A liner is a glaze for the inside food surfaces chosen for durability and resistance to leaching, running and crazing, most often a glossy clear, white or modestly coloured one. Keep runny, reactive or brightly coloured glazes for the outside.
• No crazing on food surfaces. Cracks in the glaze can harbour bacteria.
• Warning signs. A glaze that marks with cutlery, stains with coffee, dulls in the dishwasher or changes with lemon juice or vinegar is showing poor durability. Treat it with suspicion even before any test.
• Labels are a start, not proof. Makers describe commercial glazes as food safe if used according to their directions; layering, mixing or firing them another way is outside those directions.

How pottery is tested

Lead and cadmium release is measured by leaching. In the UK test, for example, the piece is filled with 4% acetic acid and left for 24 hours at about 22 °C, then a laboratory measures how much lead and cadmium the acid has taken up. The FDA's guides name ASTM method C738 and AOAC methods 973.32 and 973.82. Testing is done by a laboratory, ideally one accredited for the method; test each glaze and clay combination you use on food surfaces, and test again when you change the recipe, the clay or the firing.

The FDA describes home lead test kits: you rub a swab on the food surface and, in most kits, it changes colour if lead leaches onto it. If a kit shows lead, the FDA strongly advises against using the piece for food or drink. A swab that does not change colour proves much less: Hawaii's Department of Health notes that testing dishes for lead is difficult and that most of these kits are not recognised by the EPA for accuracy. A swab gives a colour, not a measurement against the limits below.

The legal limits for lead and cadmium

These are the limits as published on 2 November 2026. They are for ware that is sold; this page gives no legal or laboratory advice, so check the current text for your country.

From CPG Sec. 545.450 (lead) and Sec. 545.400 (cadmium), both revised November 2005. The cadmium guide has no separate cup or pitcher category, so those rows use its small and large hollowware levels. The lead guide treats a piece as unsuitable for food use if it carries both a conspicuous label and a permanent statement fired onto the base, or has a hole bored through the food surface.

In England these are in Part 4 of the Materials and Articles in Contact with Food (England) Regulations 2012, in force with no outstanding changes listed on 2 November 2026; Scotland and Wales have their own 2012 regulations with the same ceramics part. They also require a written declaration of compliance with ceramic articles up to and including the retail stage, and test documentation on request unless you can show the materials contained no lead or cadmium. In the EU the same figures come from Directive 84/500/EEC, as amended by Directive 2005/31/EC. The European Commission says it is working to lower the lead and cadmium limits significantly and to add limits for other metals; its page, updated 8 October 2026, describes this as work in progress, not adopted rules.